Gas Turbine Principles

Question 1

What is the thrust equation?

Answer 1

Thrust = mass air flow x (velocity of exhaust - true air speed) + cross sectional area of exhaust x ( jet static pressure - ambient pressure)

Question 2

What is the air that goes around the outside of a turbine called.

Answer 2

Bypass air

Question 3

Total thrust = fan thrust + blank thrust

Answer 3

Core

Question 4

Pressure thrust (Pf) can be considered when the exhaust nozzle becomes ‘blanked’

Answer 4

Chocked

Question 5

1 horse power is how much thrust?

Answer 5

2.5 pounds

Question 6

What are the 4 parts of the brayton cycle on a gas turbine?

Answer 6

Intake - compression - combustion - exhaust

Question 7

Whats the difference between the otto cycle and the brayton cycle?

Answer 7

Brayton happens all at once, continuously.

Question 8

Combustion takes place at constant blank, in a gas turbine.

Answer 8

Pressure

Question 9

Where does the highest temperature occur within the gas turbine?

Answer 9

Primary zone within the combustion chamber

Question 10

What is the highest thrust that the engine produces?

Answer 10

Static thrust

Question 11

What is a flat rated engine?

Answer 11

limited at temperature below 15 degrees

Question 12

Bleed air blanks the mass flow and thus reduces thrust.

Answer 12

Reduces.

Question 13

Intake heating systems blank the air density and so blank mass flow

Answer 13

Reduce

Question 14

What is thermal efficiency?

Answer 14

Fuel energy to kinetic energy.

Question 15

What does EPR stand for in a turbine engine!

Answer 15

Engine pressure ratio

Question 16

What is propulsive energy?

Answer 16

Kinetic energy translated into propulsive force.

Question 17

How do the gas parameters change within the stator of a compressor stage? The temperature increases, the…Pressure blanks and the speed blanks

Answer 17

Pressure increases and the speed decreases.

Question 18

Which of these statements about an impulse turbine are correct or incorrect?

I. The pressure drops across the nozzle guide vanes
II. The pressure drops across the rotor blades

Answer 18

Correct - incorrect

Question 19

In subsonic airflows, the convergent exhaust unit is designed to convert… pressure into blank

Answer 19

Speed

Question 20

The maximum temperature in a gas turbine engine is limited by the… temperature at the blank

Answer 20

Turbine.

Question 21

Both gas turbine and piston engines use a cycle made up of induction, compression, combustion and exhaust phases. Which of these statements about a gas turbine are correct?

1. The process in a gas turbine engine is continuous
2. Theoretically the combustion occurs at constant volume

Answer 21

Correct - incorrect

Question 22

Jet engine total efficiency indicates the efficiency at which… blank power is transformed into blank power

Answer 22

Chemical to propulsive

Question 23

The bypass ratio:

I. is the ratio of bypass air mass flow to HP compressor mass flow
II. can be determined from the inlet air mass flow and the HP compressor mass flow

Answer 23

Both correct

Question 24

One of the advantages of multiple-spool jet engine designs is that…a smaller air starter driving only a single blank can be used.

Answer 24

Spool

Question 25

One advantage of having three instead of two spools in some high-bypass turbofan engine is that…fewer variable stator vanes and variable inlet guide vanes are required to prevent blank stall at high/low rotor speeds.

Answer 25

Compressor at low

Question 26

To ensure efficient combustion in a gas turbine engine…it must be capable of creating the optimal blank blank blank blank.

Answer 26

Mixture of air and fuel

Question 27

The primary reason for a limitation being imposed on the temperature of gas flow in a gas turbine is to…ensure that the maximum acceptable temperature at the blank blank is not exceeded.

Answer 27

Turbine blades

Question 28

Compressor stall in a gas turbine engine is due to… an excessively high blank of the rotor blades.

Answer 28

an excessively high angle of attack of the rotor blades.

Question 29

Which of these statements is correct with regards to stator vanes within axial flow compressors? Pressure increases/decreases due to the air's blank energy being converted into pressure energy.

Answer 29

Increases kinetic energy

Question 30

IMPULSE: * Guide Vanes --> Pressure blanks * Rotor Blades --> Pressure is Constant REACTION * Guide Vanes --> Pressure blank * Rotor Blades --> Pressure Drops

Answer 30

IMPULSE: * Guide Vanes --> Pressure Drops * Rotor Blades --> Pressure is Constant REACTION * Guide Vanes --> Pressure is Constant * Rotor Blades --> Pressure Drops

Question 31

IMPULSE: * Guide Vanes --> Pressure Drops * Rotor Blades --> Pressure blank REACTION * Guide Vanes --> Pressure is Constant * Rotor Blades --> Pressure blank

Answer 31

IMPULSE: * Guide Vanes --> Pressure Drops * Rotor Blades --> Pressure is Constant REACTION * Guide Vanes --> Pressure is Constant * Rotor Blades --> Pressure Drops

Question 32

What is the purpose of an exhaust nozzle?

Answer 32

Exhaust gasses have a higher velocity

Question 33

Which of these statements about an impulse turbine are correct or incorrect? I. The pressure rises across the nozzle guide vanes II. The pressure remains constant across the rotor blades

Answer 33

Incorrect - correct

Question 34

The bypass air in a turbo fan engine has the effect of a lower specific fuel consumption by causing an overall…increase/decrease in average exhaust gas flow velocity and a higher/lower mass flow.

Answer 34

Decrease higher

Question 35

Which of these statements about compressor stall in a gas turbine engine are correct or incorrect? I. A compressor stall is most likely to occur in a compressor designed for a high pressure ratio operating at high RPM II. A compressor stall is most likely to occur when the air flow stagnates in the rear stages of the compressor

Answer 35

Incorrect - correct

Question 36

The purpose of variable by-pass valves in a high bypass turbofan engine between the LP compressor and the HP compressor (HPC) is to…prevent fan blank and LP compressor stall during engine start and blank rotor speeds.

Answer 36

Stall low

Question 37

With regard to a jet aeroplane, specific range is the… blank flown per unit fuel of mass

Answer 37

Nautical airmiles

Question 38

What is the main purpose of a diffuser? To reduce the blank of the gas entering the combustion chamber.

Answer 38

Velocity

Question 39

The function of a vibrator (trembler mechanism) in gas turbine ignition systems is to provide…

Answer 39

Dc to transformer

Question 40

When does a hung start occur?

Answer 40

Too low pneumatic

Question 41

When does a hot start occur?

Answer 41

Tail wind or early cutout